History of Modern Physics 1880-1930
Physicist Nat. date Type Description
Thomas Young 1801 Demonstrated the wave nature of light using the double-slit experiment �
Amedeo Avogadro 1811 ✏ Molecular theory of gasses. Gasses at the same temperature and volume contain the same number of molecules. Robert Brown 1827 Observed jittery motion of minute particles inside pollen grains (now called � Brownian motion but previously observed by Jan Ingenhouse in 1784) James Maxwell 1873 Developed concise equations describing electricity and magnetism (Maxwell’s ✏ equations). Predicts electromagnetic waves that travel at the speed of light.
Albert Michelson 1887 � Conducted the Michelson-Morely experiment in which he and Morley used an interferometer to show the ether does not exist.
Johannes Rydberg 1888 � Found an empirical formula describing the wavelengths of spectral lines produced by hydrogen. Rydberg constant is named for him. Wilhelm Röntgen 1895 Produced and detected x-rays (also called Röntgen rays), a new form of � electromagnetic radiation. 1901 Nobel Prize. Pieter Zeeman 1896 Discovery of Zeeman effect. Many spectral lines can be sllit into multiple lines � in the presence of a magnetic field. 1902 Nobel Prize.
Henri Becquerel 1896 � Discovery of radioactivity. 1903 Nobel Prize (shared with Marie and Pierre Curie).
J.J. Thomson 1897 � Discovery of the electron. Cathode ray experiments showed the rays are made of particles (electrons) ejected from atoms in the electrodes. 1906 Nobel Prize. Marie Curie 1898 Discovery of radioactive elements Polonium and Radium. 1903 Nobel Prize � (shared withe Becquerel and Pierre Curie). Ernest Rutherford 1899 Discovery of alpha and beta rays. Showed that uranium gives off two kinds of � radiation.
Paul Villard 1900 � Discovery of gamma rays. Showed that this form of radiation from radioactive decay was not electrically charged, but could not penetrate as far as x-rays.
Lord Rayleigh 1900 ✏ Derivation of Rayleigh-Jeans law of radiation from a blackbody using thermo- dynamics. Extension to short wavelengths led to the “ultraviolet catastrophe” Max Planck 1900 Blackbody radiation formula. Assumed quantized energies for light waves ✏ E = h f, where h is Planck’s constant. Resolved ultraviolet catastrophe
Hendrick Lorentz 1904 ✏ Derived the Lorentz transformation to relating observers’ measurements of space and time (later becomes part of Special Relativity). 1902 Nobel Prize. Albert Einstein 1905 Theory of Brownian motion: random motions are due to collisions with ✏ molecules Albert Einstein 1905 Theory of photoelectric effect: electromagnetic waves act like particles. 1921 ✏ Nobel Prize.
Albert Einstein 1905 ✏ Special theory of relativity. One’s measurements of space and time depend on one’s relative motion to another observer. Equivalence of mass and energy
Robert Millikan 1909 � Millikan oil drop experiment. Measurement of the charge of the electron using falling oil drops in electric field. 1923 Nobel Prize. Charles Wilson 1911 Invention of the cloud chamber. Photographed particle tracks for α and β � particles. 1927 Nobel Prize (shared with Compton). Ernest Rutherford 1911 Rutherford scattering of alpha particles from a gold foil. Evidence for atomic � nucleus and the proton. William L. Bragg 1912 Bragg diffraction. Showed that x-rays exhibit diffraction patterns when they � pass through crystal lattices. Analyzed crystal structure. 1915 Nobel Prize.
Niels Bohr 1913 ✏ Bohr-Rutherford model of the atom. Electrons orbit central nucleus with quantized angular momenta. Reproduces Balmer spectrum. 1922 Nobel Prize. Albert Einstein 1916 General theory of relativity. Extends special relativity to include gravity and ✏ accelerating reference frames. Arthur Compton 1922 Compton effect. Showed that x-rays act like particles when they scatter off free � electrons. 1927 Nobel Prize (shared with Wilson). Luis de Broglie 1922 Proposed wave nature of matter, thus creating field of wave mechanics. ✏
Wolfgang Pauli 1925 ✏ Formulated the Pauli exclusion principle, which says that no two electrons can exist in the same quantum state. Werner Heisenberg 1925 Development of matrix mechanics, which was the first formalization of quantum ✏ mechanics. 1932 Nobel Prize. Erwin Schrödinger 1926 Wave mechanics approach to quantum physics. Schrödinger equation. Wave ✏ functions for hydrogen atom, harmonic oscillator. 1933 Nobel Prize. Max Born 1926 Probabilistic interpretation of wave function. 1954 Nobel Prize. ✏
George Thomson 1927 � Demonstrated wave nature of electrons by diffracting them through gold foil. 1937 Nobel Prize. George Uhlenbeck 1927 ✏ Theoretical discovery of electron spin (with Samuel Goudsmit ). Provided explanation of doublets in spectral lines. Werner Heisenberg 1927 Uncertainty principle. Measurement of one paired physical quantity (e.g. ✏ position) introduces uncertainty in the other (e.g. momentum). Paul Dirac 1928 Dirac equation: extension of Schrödinger equation to includes special relativity. ✏ Explanation of electron spin and predicts antimatter. 1933 Nobel Prize.
Carl Anderson 1932 � Experimental discovery of antimatter (positron). Found particle tracks of positrons (produced by cosmic rays) in a cloud chamber. 1936 Nobel Prize. James Chadwick 1932 Discovery of the neutron. 1935 Nobel Prize. �
Otto Stern 1933 Stern-Gerlach experiment. Measured magnetic moment of the proton. � Experimental verification of space quantization. 1943 Nobel Prize.
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Type of discovery: ✏ Theoretical discovery � Experimental discovery